(1) Field of the Invention
This invention relates to a telephone terminal equipment which attains an audio call corresponding to audio signals transferred through one of plural networks including a telephone network and an Internet network.
(2) Background Art
Among present telephone terminal equipments wherein an audio call is held through a telephone network, some telephone terminal equipments comprise a transfer function to attain an audio call between a first and second telephone terminal equipments after invoking the second telephone terminal equipment during an audio call with the first telephone terminal equipment.
Recently, there are telephone terminal equipments which can have audio calls through an Internet network widely available. It can make an audio call more convenient if an audio call is transferable to a telephone terminal equipment connected to an Internet network as well as to a telephone terminal equipment connected to a telephone network with above-mentioned transfer function of known telephone terminal equipments.
This kind of transfer function can be achieved, as the following describes, by changing some parts of the constitution attaining an audio call between a telephone terminal equipment connected to a telephone network and a telephone terminal equipment connected to an Internet network.
One constitution is suggested in Unexamined Japanese Patent Publication No. 7-212494 (in page 5) as an example of the constitution to attain an audio call between a telephone terminal equipment connected to a telephone network and a LAN terminal equipment connected to an Internet network; while a telephone network (a public network) and an Internet network (a LAN network) are connected by a connection control unit, the connection control unit sends a call (a connection request) from a telephone terminal equipment connected to a telephone network to a LAN terminal equipment connected to an Internet network, the connection control unit receives a transfer message from the terminal equipment connected to an Internet network, the terminal equipment to which the call is provided is changed to another terminal equipment required by the transfer message. A transfer from a terminal equipment connected to a telephone network to another terminal equipment connected to an Internet network can be achievable, with the constitution described above, by arranging the connection control unit so that any of these terminal equipments can receive a transfer message during an audio call held between two terminal equipments.
This constitution, however, only attains to switch over lines from the line of a terminal equipment which receives a transfer message to the line of another terminal equipment when a connection control unit receives a transfer message from a terminal equipment. This constitution is not applicable for an audio call among three terminal equipments; another terminal equipment connected to an Internet network is added to an audio call between two terminal equipments.
One of the objects of the present invention is to provide a telephone terminal equipment applicable for an audio call among three terminal equipments by adding another terminal equipment connected to an Internet network to an audio call between two terminal equipments, also to provide a terminal control program applicable for the telephone terminal equipment.